This master thesis has been performed at Vattenfall Power Consultant in Gothenburg and Trollhättan for Vattenfall Vattenkraft. In this report vacuum circuit breaker in small-scale hydropower stations with the rated power 4 MVA and below has been studied. Models of the stations are modeled and analyzed in PSCAD/EMTDC to study the high voltage transients that are created after Current chopping with vacuum circuit breaker. Vacuum circuit breaker may chop the current before it reaches zero value, which means that high voltage transients can be created. The equipment of the stations can be destroyed by high voltage transients.The purpose of this thesis is to examine the use of vacuum circuit breaker in small-scale hydropower stations and the risk for high voltage transients from Current chopping.According to the results there is a risk of high voltage transients after Current chopping with small synchronous generators in stations with the operating voltages 0.4 kV and 3.6 kV.

The conditions for a good silage process start with good wheather and choice of crop, then choice of harvesting machinery. The shorter and more mechanically treated crop, the better quality of the forage. (Pauly 1994). This study has examined the variations in chopping length depending on harvest method. Precision choppers works with a rotating chopping cylinder, where the crop is cut into pieces.

This paper deals with the question of with witch tools the Alvastra pile dwelling was built. To reach a result I calculate the curvature on 29 stone axes, 8 double-edged axes and 21 simple-edged axes, used in the middle-neolithic in what today is Sweden. These results are then compared with two jams (the point in the pole where the axes edged stopped and left a mark) on two piles from Alvastra pile dwelling..

Normally the operational amplifier is used as a component in active filter design. The goal for future components in filter design is large bandwith and the use of low supply voltages. The use of current-mode instead of voltage-mode circuits gets a step closer to the required performance. A component that use current as the signal conveying part is the current conveyor. In this report a comparative study between two current conveyor structures of second generation (CCII) is performed.

Until 2020, 49% of Sweden's use of energy must derive from renewable sources. Greenhouse gases must as well decline with 40% compared to 1990 as a part of Sweden's 16 environmental objectives. Biogas is part of the effort to achieve these objectives, but as the demand for biogas increases, more substrates are needed to meet the demand. The purpose is to investigate the conditions for pea residue as substrate by performing lab-scale mesophilic digestion with different fractions and notch lengths and then to summarize pea residue as a substrate for biogas production. During anaerobic digestion, 1000 ml bottles were used as reactors for digestion.

A current conveyor is an active building block that can be used to implement most active and passive components. It differs from the operation amplifier in that it uses current instead of voltage. The current conveyor also has significantly higher voltage gain over a broader frequency range. To simplify the construction of analogue circuits and increase the construction efficiency it is desirable to use a top-down methodology. This means that the whole system is partitioned into a hierarchy of subsystems.

A study was made to evaluate how current measurementscould help to determine how particles from fish farms are dispersed. During sixweeks of the summer 2012, two different current measurements were conducted.One of them consisted of measurements each fifth minute at 5 m and 15 m atthree locations for 14-16 days each. The other consisted of profilemeasurements at each location at four times during the period of six weeks. Forthe current measurements two instruments (model RCM 9) were used. A two weekmeasurement can give enough data to make an evaluation of how the currents at alocation will transport litter from a fish farm.

This thesis work is about how technical consulting companies can accept their organization before a coming recession. Technical consulting companies are together with the rest of the actors in the construction business constantly depended on the current economic situation on the market. How to adapt the organisation depends on the current situation on the market.To adapt the organization in the best way possible the companies need to recruit and educate personal. It is then very important to find a solution on how the current change of generation in the companies will be handled. The large and very much competent group of 40-talists will in a few years retire.

Through a thorough analysis of the current situation, we have highlighted differences inworking methods for the various workshops and drew up proposals for improvements incombination with a practical work description that can be implemented in the company..

The aim with this literature review is to describe the ensilage process in a bunker silo. The process from harvest and chopping to filling and unloading the silo is explained. The sealing of the bunker silo plays an important role for the final quality of the silage. This review covers some of the techniques used. There are many silage additives on the market, some of them are presented including how they act in the ensilage process.

Mechanical relays are more and more being replaced with semiconductortechnology. In this thesis it is investigated if and how the larger loads couldbe controlled by transistors. The main part of this work aims to create andverify a solution that can control the starter motor, as well as protect it incase of any failure. The different malfunctions that the solution protectsagainst is high current, too high peak current, low current, maximum cranktime and minimum cool off time. The timers also protect indirectly againstoverheating of the starter engine.The transistors used are BTS555, from Infineon.

We got in contact with Marco AB, who we?ve had contact with before concerning earlier projects, to find out if they were interested in arranging a larger project for our last class (Examensarbete 15hp). They were very positive to this proposition, and soon they offered us a project regarding reconstruction of their current mechanical device that absorbs all the force from the lift itself when it is at a predefined level (sv. sjunkspärr). The current solution does fulfill the requirements that are given, however it is not a solution that gives a high level of satisfactory.

The purpose of this thesis is to examine whether the concept of permanent establishment, as defined in Article 5 of the OECD Model Tax Convention on Income and Capital, is applicable to electronic commerce and if so whether the current definition is able to appropriately deal with the challenges of electronic commerce.In 2003, the OECD added a new section to the Commentary on the Model Tax Convention on Article 5. The new section is a clarification on the application of the permanent establishment definition in electronic commerce.The current definition of permanent establishment in the Model Tax Convention relies on the physical presence of a foreign corporation as the threshold for source taxation. While the current definition, prima facie, might be applicable on electronic commerce, the highly mobile nature of electronic commerce might affect the current revenue distribution equilibrium between states..

Storing kinetic energy in a flywheel allows for more efficient driving of electricvehicles. Research in this area is in progress at Uppsala University, where a flywheelwith magnetic bearings encased in a vacuum chamber is being constructed. To makethis possible methods for measuring the current through the electromagnets in thebearings and temperatures in the flywheel need to be developed. This has been thepurpose of this report. The current measurement resulted in a resistive method, andthe implementation of eight measurement circuits in the system.

We got in contact with Marco AB, who we?ve had contact with before concerning earlier projects, to find out if they were interested in arranging a larger project for our last class (Examensarbete 15hp). They were very positive to this proposition, and soon they offered us a project regarding reconstruction of their current mechanical device that absorbs all the force from the lift itself when it is at a predefined level (sv. sjunkspärr). The current solution does fulfill the requirements that are given, however it is not a solution that gives a high level of satisfactory.